How do I recover a semaphore when the process that decremented it to zero crashes?

Question

I have multiple apps compiled with g++, running in Ubuntu. I\'m using named semaphores to co-ordinate between different processes.

All works fine except in

Answer 1

This is a typical problem when managing semaphores. Some programs use a single process to manage the initialization/deletion of the semaphore. Usually this process does just this and nothing else. Your other applications can wait until the semaphore is available. I've seen this done with the SYSV type API, but not with POSIX. Similar to what 'Duck' mentioned, using the SEM_UNDO flag in your semop() call.

But, with the information that you've provided I would suggest that you do not to use semaphores. Especially if your process is in danger of being killed or crashing. Try to use something that the OS will cleanup automagically for you.